A friend bought it not-running after previous owners were unable to get it running. It sat for "a few years". Someone worked on the wiring: the ICU was unplugged; FI relay case open, loose wires under the dash, ...

It runs now via some new/used parts: fuel pump, fuel filter, white-label 951, FI relay, plugs, cap, wires, coil, intake manifold gasket, bellows, vacuum lines, FPR, O2 sensor, timing belt, IAV cleaned, throttle body cleaned, grounds removed, cleaned, reinstalled, good used MAF, TPS clicks, cat's not clogged, power stage stays cool, ...

Problems: starts and stalls 2-3 times (when motor cold) before it'll stay running; rough idle when motor is warm; poor MPG, black tailpipe, black smoke idling. Drives smoothly, has decent power.

Codes:
o 1-2-3 ECT
o 1-1-3 Fuel Injector Signal
o 1-2-1 Failed signal to/from AMM (MAF)

1. I pulled the IAV (2-wire) and tested again. It clicks on the bench but not when it's hooked up in the car. Wires from the IAV are OR (orange) and GN-R (green w/ a red stripe). In Bentley (p 241-6) it looks like the OR joins the injector wires in the junction under the intake manifold; GN-R goes to the ICU.

Hooking a test light between a battery post and the IAV plug I got:
- Key off: both wires lit the test light when hooked to bat + (indicating they are grounded)
- Key on (engine not running): OR lit the test light when hooked to ground. Otherwise nothing.

I expected the GN-R wire to show 12V. The wiring harness looks intact. The OR wire broke inside the harness and made contact with 12V? I believe 1 black or brown ground wire goes back from the wire cluster to the ICU.

It'll be easy to run a new ground from the IAV to the intake manifold but if there's no power on the GN-R wire ...?

2. The intake-manifold gasket I replaced was intact but showed signs of leaking - dark areas in the center. Perhaps the intake manifold is warped.

3. It's possible that the MAF is failing and/or O2 sensor is fouled/failed.
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240 drivers / parts cars - JH, Ohio

"o 1-2-1 Failed signal to/from AMM (MAF)"

First thing I'd do is switch in another MAF (AMM). They tend to go wrong.

"I pulled the IAV (2-wire) and tested again. It clicks on the bench but not when it's hooked up in the car." and
"- Key on (engine not running): OR lit the test light when hooked to ground. Otherwise nothing."

So there's no voltage at the IAV plug (between GN-R and OR) with the key on?

"In Bentley (p 241-6) it looks like the OR joins the injector wires in the junction under the intake manifold; GN-R goes to the ICU."

Yes. page 19.
http://www.volvowiringdiagrams.com/volvo/240%20Wiring%20Diagrams/Volvo%20240%201989.pdf

If you're going to cut open the harness to trace connections, it might be a good idea to move the injector wires so they approach from above rather than below the manifold. (Giving more room below.)

"It's possible that the MAF is failing and/or O2 sensor is fouled/failed."

It's easy to check O2 sensor operation with a voltmeter between it and ground.



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1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

Thanks for the reply.

- First thing I'd do is switch in another MAF (AMM). They tend to go wrong.

JH: Yes, tried my spare MAF and pulled the one from my driver - no change.



- So there's no voltage at the IAV plug (between GN-R and OR) with the key on?

JH: Key on, there's voltage on the OR IAC ground wire. This is what's confusing me. If there is voltage on the OR wire, it can't be grounded to the manifold as shown in Bentley. I'm going to check that again today.

The lack of voltage on the GN-R wire could be a fail at the ICU or FI relay. I'm going to reflow joints on a relay to eliminate that possibility.


- If you're going to cut open the harness to trace connections ...

JH: I've cut open 2-3 engine-area harnesses on > 1988 cars and never found a problem. So that's a last resort. If the harness was older, or looked like it'd been tampered with, I'd cut it open. I may pull the intake manifold, test/replace the (new) ECT, and explore some in the harness anyway.


- It's easy to check O2 sensor operation with a voltmeter between it and ground.

JH: I got readings within range on this O2 sensor but I don't trust my muiltimeter and/or my skill with it. I know it's easy but I've had bad O2 sensors give OK readings and good ones give bad readings - operator error I'm sure.
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240 drivers / parts cars - JH, Ohio

Haven't posted this recently, but some say it helped them...

Start-Run Sequence LH 2.4

1) During starter cranking, the Crank Position Sensor (CPS) sends timing pulses to the Ignition Control Unit (ICU).

2-a) The ICU sends these CPS pulses to the Power Stage (aka Ignition Amplifier), to initiate spark voltage pulses from the coil.

2-b) At the same time, the ICU also propagates these CPS-based pulses to the Fuel ECU to allow FI operation (no ICU pulses means no FI operation).

3-a) The Fuel "System"* relay (previously energized at Key On) sends 12V power to the:
• Fuel ECU,
• Fuel (pump) relay coil + side (ECU controls coil ground)
• Idle Air Control valve (IAC) (ECU controls coil ground)
• 700/900 only, the Radio Suppression Relay (RSR), which in turn powers the + side of the Injectors. (injector ground side controlled by the ECU)

* The System (aka Main) relay is in the white case with the Fuel pump relay.

3-b) When ICU pulses are received by the FI ECU, it "energizes" the Fuel pump relay by grounding the relay coil (– side) to power the fuel pump.

When all these things work, the engine runs until the Ignition is switched off, which in turn shuts down the FI system.

==============================

The RS Relay powers the injectors and (on 7/9 turbos) the coil as well.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Thanks. I've see it and might have it stored somewhere but I just made another copy. It's a good summary of what happens and how to look for problems.
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240 drivers / parts cars - JH, Ohio

Have you tried another ignition amplifier? The poor running may be due to weak spark.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

Yes, I have 2 spare ones I swap around and it made no difference.
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240 drivers / parts cars - JH, Ohio

"In Bentley (p 241-6) it looks like the OR joins the injector wires in the junction under the intake manifold; GN-R goes to the ICU."
• You lost me there, Jon. That page in my (old) Bentley is all about LH OBD, but nothing on wiring. But what you say is correct, the OR wiring originates at the System relay and takes operating voltage many places, including the injectors. The ECU controls the ground side as required, i.e. for pulsing the injectors.

"JH: Key on, there's voltage on the OR IAC ground wire. This is what's confusing me. If there is voltage on the OR wire, it can't be grounded to the manifold as shown in Bentley. I'm going to check that again today."
• Yes, check that again. The OR wire is Key-On powered from the system relay. Grab a magnifying glass and you'll see it on Bentley page 390-46, grid blocks K4, K5 and L4, L5.
It starts in L5 at item 217, which Bentley calls the "Main" relay, which shared the white case with the Fuel (aka Pump) relay.

--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Right, 241-6 is the Bentley page with the fault-codes table. Sorry about that*. Yes, I meant 390-46, starting block K-4. And I see now: OR goes to 217 "Main relay" (and other places) and GN-R goes to 214 "Control unit".**

So, I'll test the IAC "Air Control Valve" (Bentley 241-20) and I'll see if I get a pulse on the GN-R ground coming from the "Control Unit". If there's no pulse, I'll look for a fail of the GN-R wire between the IAC connector and Control Unit.

If the IAC works and the hard-starting/ running-rich conditions remain, I'll

- Reflow the solder joints on the Main Relay (good idea to do that anyway)

- Retest the O2 Sensor

- Test the new ECT (old message from you about not using teflon sealer)

- Test the TPS

- Check new intake-manifold gasket. Old one looked good but showed signs of leaking. Perhaps a warped intake manifold?

- Swap in a spare 951 control unit. The car had an episode of overcharging (failed diode?) and I replaced the alternator.

(Oddly: the hard starting (motor cold) was cured by a new distributor cap for a week or so; then it came back.)

Thanks for taking the time to comment Bruce. I wasn't paying enough attention to the book.

--------------------------------------------
*I bought some magnifying glasses specifically to read Bentley & Haynes diagrams but I wrote the page # down (instead of bringing the book in with me) last night and didn't notice it'd flipped back.

**Not sure how I mixed all this up as I worked on a 1990 last year and found a broken orange wire to one of the injectors
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240 drivers / parts cars - JH, Ohio

Might still be the ECT sensor for the computer. It could be telling the ECU it colder than blazes of hell outside. It's under the very back intake runner.

It could be a bad sensor or unplugged. Who knows the plug to it might be on the IAC valve. Could explain the reason for no power going into the IAC as it would not be 12volt.

Do not know if they are switchable but the symptoms for me point in the ECT neck of the woods. Might read back both of the component clips to the ECU to check circuits plus any grounds under the dash.

Phil

I had another thought! Try disconnecting the return line to the fuel tank from the FPR. Blow compressed air down through it with the gas cap off. Just want to know that all of the gas that gets rejected from the FPR can get back there.

Thanks for the suggestions.

- Might still be the ECT sensor for the computer.

JH: I've replaced it but, sure could still be bad.


- It could be a bad sensor or unplugged.

JH: I cleaned the wire ends when I replaced the ECT and it's snug.



- Who knows the plug to it might be on the IAC valve.

JH: The ECT, IAC and cold-start injector all have 2-prong plugs. Knowing this, I compared the wires inside the boot against Bentley and I checked the color-coded boot (1 black, 1 blue, 1 yellow) against my 240 driver. But yesterday I checked: the IAC has OR & GN-R wires and this matches Bentley.

I have mixed TPS and 3-wire IAC plugs. Ran it a few minutes that way and didn't fry a circuit, as Art B suggested can happen.


- Might read back both of the component clips to the ECU to check circuits

JH: Good suggestion, I'll try this.


- plus any grounds under the dash.

JH: I think there's only one relevant ground at the ICU but I'll check again. The key grounds are the two on the intake manifold. Another post suggests replacing connector ends and soldering them on.


- Try disconnecting the return line to the fuel tank from the FPR. Blow compressed air down through it with the gas cap off.

JH: Did that early on and heard it bubbling in the tank. The sender is new, lines look good eg. no visible kinks/crushes.
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240 drivers / parts cars - JH, Ohio